This is a textbook question - found on Page 183 Exercise 6.4.2

For each of the following exercises construct 90, 95, and 99 percent confidence intervals for the difference between populations means. When appropriate state the assumptions that make your method valid. State the practice and probabilistic interpretations of each interval that you construct. Consider the variables under consideration I reach exercise and state what use you think researchers might make of your results

Chan et al. developed a questionnaire to asses knowledge of prostate cancer. There was a total of 36 questions to which respondents could 'agree' or disagree' or 'don't know'. Scores could range from 0 to 36. The mean scores for caucasians study participants was 20.6 with a standard deviation of 5.8. The mean score for African American men was 17.4 with a standard deviation of 5.8. The number of caucasian study participants was 185, and the number of African Americans was 86.